Effect of the Physical Properties of Isoflurane, Sevoflurane, and Desflurane on Pulmonary Resistance in a Laboratory Lung Model

Background: Airway resistance depends not only on an airway's geometry but also on flow rate, and gas density and viscosity. A recent study showed that at clinically relevant concentrations, the mixtures of volatile agents with air and oxygen and oxygen-nitrogen affected the density of the mixture. The goal of the current study was to investigate the effect of different minimum alveolar concentrations (MACs) of three commonly used volatile agents, isoflurane, sevoflurane, and desflurane, on the measurements of airway resistance.

Methods: A two-chamber fixed-resistance test lung was connected to an anesthesia machine using the volume control mode of ventilation. Pulmonary resistance was calculated at baseline (25% oxygen in air); at 1.0, 1.5, and 2.0 MAC; and also at the same concentrations, 1.2% and 4%, of isoflurane, sevoflurane, and desflurane mixtures with 25% oxygen in air. The analysis of variance test for repeated measures and probabilities for post hoc Tukey and least significant difference tests were used.

Results: Isoflurane affected pulmonary resistance only at 2 MAC. Sevoflurane caused a significant increase of pulmonary resistance at 1.5 and 2 MAC, whereas desflurane caused the greatest increase in pulmonary resistance at all MAC values used. At 1.2% concentration, no difference from the baseline resistance was observed, whereas at 4%, the three agents produced similar increases of pulmonary resistance.     

Central Aortic Stiffness in Patients With Nonischemic Dilated Cardiomyopathy: Relationship With Neurohumoral Activation

BackgroundIncreased aortic stiffness has been found in heart failure (HF), but the underlying mechanisms remain to be elucidated. The aim of the present study was to examine the association between aortic stiffness and neurohumoral activation in patients with nonischemic dilated cardiomyopathy (NIDC).Methods and ResultsWe examined 101 patients with NIDC, New York Heart Association Class II-III, LVEF 33.3 ± 11.6%, and 33 controls. All subjects underwent blood sampling for plasma concentrations of renin, aldosterone, C-reactive protein (CRP), and brain natriuretic peptide (BNP). We evaluated the pulse wave velocity (PWV) of the proximal aorta in the region of the aortic arch with a new echo application. Patients showed increased PWV (P < .001), and increased plasma levels of log-renin (P < .001), log-aldosterone (P = .01), CRP (P = .01), and log-BNP (P = .01) compared with controls. PWV was correlated with log-BNP (r = 0.63, P < .001) and log-aldosterone (r = 0.34, P < .001) levels, with LV end-diastolic (r = 0.27, P = .01) and end-systolic (r = 0.33, P = 0.003) volumes, and the PW-tissue Doppler imaging systolic wave (r = –0.27, P = .006) and the E/e′ ratio (r = 0.45, P < .001). Linear regression analysis showed that log-BNP levels were independently associated with PWV.ConclusionsIn patients with HF from NIDC, there is evidence of increased aortic stiffness that is correlated with LV shape and function. Although aldosterone levels seem to influence the aortic PWV, BNP levels are the best independent predictor of increased PWV.     

Effect of the physical properties of isoflurane, sevoflurane, and desflurane on pulmonary resistance in a laboratory lung model

BACKGROUND: Airway resistance depends not only on an airway's geometry but also on flow rate, and gas density and viscosity. A recent study showed that at clinically relevant concentrations, the mixtures of volatile agents with air and oxygen and oxygen-nitrogen affected the density of the mixture. The goal of the current study was to investigate the effect of different minimum alveolar concentrations (MACs) of three commonly used volatile agents, isoflurane, sevoflurane, and desflurane, on the measurements of airway resistance. METHODS: A two-chamber fixed-resistance test lung was connected to an anesthesia machine using the volume control mode of ventilation. Pulmonary resistance was calculated at baseline (25% oxygen in air); at 1.0, 1.5, and 2.0 MAC; and also at the same concentrations, 1.2% and 4%, of isoflurane, sevoflurane, and desflurane mixtures with 25% oxygen in air. The analysis of variance test for repeated measures and probabilities for post hoc Tukey and least significant difference tests were used. RESULTS: Isoflurane affected pulmonary resistance only at 2 MAC. Sevoflurane caused a significant increase of pulmonary resistance at 1.5 and 2 MAC, whereas desflurane caused the greatest increase in pulmonary resistance at all MAC values used. At 1.2% concentration, no difference from the baseline resistance was observed, whereas at 4%, the three agents produced similar increases of pulmonary resistance. CONCLUSION: High concentrations of volatile agents in 25% oxygen in air increased the density of the gas mixture and the calculated resistance of a test lung model with fixed resistance.     

The origins of oral medicine in the Hippocratic collected works

The collected works of Hippocrates describe for the first time in a systematic way a large number of oral diseases, such as ulcers, inflammations, abscesses and tumours from the epiglottis, mouth, tongue, palate, uvula and the sublingual area. Several of these case reports are remarkable for the accurate observation of clinical symptoms and signs, the aetiology, the pathogenesis and their therapeutic approach in relation to prognosis. The Hippocratic authors report cases of aphthae as part of a polysystemic disease, described many centuries later by Behçet and Adamantiades, while they associate features of splenomegaly from endemic malaria with gingivitis (ulitis). Benign lip ulcers, caused by sharp teeth bites, were distinguished from the difficult to treat herpes labialis (herpes) and from the necrotising nomae. Although staphylitis and angina (kynanche) were attributed to phlegm accumulation, they were recognised as true emergencies when they were associated with a swollen tongue and uvula. Several cases of kynanche with forward displacement of the first cervical vertebrae, atrophy of the uvula and oedema of the jaws are illustrated. A fatal outcome was anticipated in cases of phagedaenic ulcers of the teeth, causing necrosis and abscess formation. The therapeutic approach of oral diseases proceeded step by step, starting with simple regimens and progressing to invasive techniques, such as phlebotomy, surgical incisions for fluid drainage, and cauterisation. With the aim to avoid adverse events, special attention was paid to the correct timing of surgery and the maintenance of a patent airway with the insertion of small pharyngeal tubes.     

Atrial natriuretic peptide in children with idiopathic hypercalciuria

We measured plasma atrial natriuretic peptide (ANP) levels in 30 children with idiopathic hypercalciuria (IH) and 19 normal controls (NC). A calcium (Ca) loading test was performed in all patients to determine the type of IH. Subsequently plasma ANP, cAMP and renin activity (PRA), serum total and ionized Ca, intact parathyroid hormone, aldosterone, and 1,25-dihydroxyvitamin D as well as urine Ca, cAMP, and electrolytes were determined in all subjects. The mean (SD) plasma ANP levels were significantly lower in patients with renal hypercalciuria (RH) [21.4 (4.8) pg/ml] than in those with absorptive hypercalciuria (AH) [26.8 (7.6) pg/ml, P<0.05] and NC [27.6 (6.6) pg/ml, P<0.01]. PRA was significantly lower in AH [2.9 (1.3) ng/ml per hour] than in RH patients [7.8 (6.8) ng/ml per hour, P<0.01] and in NC [6.8 (4.6) ng/ml per hour, P<0.005]. Serum aldosterone values were significantly lower in AH [14.5 (11.4) ng/dl] than in RH patients [25.4 (14.1) ng/dl, P<0.05] and in NC [32.6 (20.5), P<0.001]. The lower plasma ANP levels in RH than in AH patients and in NC may be due to Ca depletion. The lower PRA and serum aldosterone levels in AH than in RH patients and in NC may be attributed to Ca excess. Received: 18 November 1998 / Revised: 4 October 1999 / Accepted: 5 October 1999     

NT-proBNP response to dobutamine stress echocardiography predicts left ventricular contractile reserve in dilated cardiomyopathy

BACKGROUND: Brain natriuretic peptide (BNP) and left ventricular (LV) inotropic reserve are major prognostic indexes in heart failure (HF). AIMS: To investigate the relationship between N-terminal-proBNP (NT-proBNP) changes in response to dobutamine stress echocardiography (DSE) and the LV inotropic reserve, in HF patients with dilated cardiomyopathy (DC). METHODS: We studied 41 patients with DC, LVEF 31.6+/-7.7%, NYHA class II-III and 15 controls. Plasma NT-proBNP levels were measured before and 60 min after three 5-min stages of dobutamine (5 to 15 microg/kg/min). RESULTS: Based on NT-proBNP changes in response to dobutamine, patients were categorized into two groups: In Group A circulating NT-proBNP levels fell (-16.6+/-7.8%), and in Group B they increased (8.4+/-9.1%). Group A had a marked improvement in WMSI compared to Group B (32.1+/-9.7% vs. 18.8+/-15.9%, p<0.001). Multivariate analysis showed that NT-proBNP changes were an independent predictor of LV inotropic reserve (b= -0.55, p<0.001). A reduction of 21.3% in plasma NT-proBNP levels in response to dobutamine predicted an improvement in WMSI of >25% with a sensitivity of 100% and a specificity of 92.3%. CONCLUSIONS: NT-proBNP changes in response to dobutamine reflect improvement in LV contractility and constitute an independent predictor of LV inotropic reserve in patients with DC.